Piston packing



Patented Nov. 27, 1934 PATENT ori-ics PISTON PACKING Ralph A. Light, Cynwyd, and Joseph W. Price, Jr.,

Philadelphia, Pa., assignors to The U nlted States Metallic Packing Company, Philadelphia, Pa., a. corporation of Pennsylvania Application July 24, 1933, Serial No. 681,917

6 Claims.

This invention relates to piston packings; and it has reference more particularly to piston packings for power reverse gears used on steam locomotives.

A recent ruling of the Interstate Commerce Commission requires that all steam locomotives over a certain weight be equipped with power reverse gears, and further that, in addition to the connections for compressed air by which such reverse gears are usually operated, the installation of steam connections to the locomotive boilers so that, in the event of breaks in the air lines, it is possible to operate the gears with steam and thus enable control of the locomotives through reversal in the operation of their valve motions, with the main cylinders acting after the manner of air compressors, to gradually reduce the speed of the locomotives and thereby finally bring the trains to a stop. The composite asbestos and rubber piston packings heretofore generally employed in reverse gears, while satisfactory for compressed air operation, are entirely unsuited for steam operation by virtue of the fact that they disintegrate under the heat of the steam with resultant leakage of the steam past the pistons, thereby allowing the latter to creep with attendant mal-operation of the reverse gear as a whole.

In the main, our invention is directed toward overcoming the above mentioned drawbacks, that is to say, we aim to provide a simple, inexpensive and easily replaceable packing which is espey cially suited -for pistons of Ilocomotive reverse gears, which will edectively resist the action of heat when steam is employed as the motivating pressure medium, and which moreover can be relied upon for maintenance of a substantially perfeet fluid-tight seal between the pistons and the surrounding Walls loi the actuating cylinders of such gears.

A further aim of our invention is to secure the foregoing advantages in a packing which can be used in connection with the standardized pistons ci power reverse gears for locomotives without requiring any structural changes whatever either in the pistons or the cylinders oi' said gears.

Still other objects and attendant advantages of this invention will be manifest from the following detailed description of the accompanying drawing, wherein Figure I is a face View of a v locomotive valve gear 'piston embodying our improved packing.

Fig. IIis an axial section oi the piston taken as indicated by the arrows II-II in Fig. I; and,

Fig. III shows theedge view of a sealing ring which constitutes a part of the packing.

In Figs. I and II oi these illustrations, the piston is comprehensively designated by the numeral vt; while the reverse gear actuating cylinder in which the piston reciprocates, is indicated in part at 5 in Fig. II only. The body mem- 60 v ber 6 of the piston 4 is of a standardized type designed for attachment of reversely positioned cup packings which have been generally employed in this'. art heretofore, said body member being formed with the characterizing annular peripheral shoulder '7 and being secured to the tapered end 8 of the axially-connected piston rod 9 by means of a jamb nut l0. The packing with which the present invention is more especially concerned comprises a bull ring 1l, and a follower ring 12 both of which are accurately machined to closely :fit the bore of the cylinder as well as to nt over the horizontal face 13 of the angular circumferential shoulder 'l of the body member 6. As shown in Fig. II, the 75 bull and follower rings l1 and 12 jointly afford a circumferential groove 14 to receive, with a certain amount of side clearance at 15, 15, a sealing ring 16 which has astepped split at 17 in Fig. III. Also, as shown, the sealing Ting 16 is peripherally 80 grooved at 18 to reduce its bearing area in contact with the cylinder wall, and to provide chan- A nels for lubrication. The depth of the groove 14, it will be 'noted from Fig. II, is such as to provide internally of the sealing ring 16, an annular interval into which we place soit resilient fibrous packing material such as conventionally shown at 19. On its inner face, the follower ring 12 has a circular recess 20 to accommodate an expander ring 21 which is so proportioned as to 90 determine a circumferential clearance 22 between it and the inner periphery of the sealing ring 16 for a purpose later on explained. A numher of helical springs 23 concealed within axial cavities 24 oi bosses 25 at intervals around the 95 follower ring 12 and held in compression by yheadeddxeeper screws 26, serve to yieldingly urge the expander ring 2l laterally against the soft resilient packing material 19. The packing material 19 ls thereby caused to completely lill the 100 annular space immediately, within the ring 16, and at the same time to press outwardlyV and expand said sealing ring yieldingly into fluidtight contact with the wall of the cylinder 5. As illustrated, the bull and follower rings 1l and12 ,105 are suitably apertured for the purposes of lightness and for the passage of the usual stud bolts 27 on-the body member 6 of the piston 4, and secured to said body member by nuts 28 engaging the threaded outer ends of said stud bolts. In- 

